A banker who claimed that he was dismissed for being “too successful” could be awarded an £11 million payout after winning a five-year battle against his former employer.

Raphael Geys, former managing director of European fixed income sales for Société Générale, will be able to claim damages for wrongful dismissal after the Supreme Court found in his favour.

He had already argued his case in the High Court and Court of Appeal, and judges have finally found in favour of his claim that he was let go without cause.

His lawyers added that he could now be entitled to a termination payment of approximately €12.5 million (£11 million), with further claims of another “several million” euros.

Mr Geys, who was employed by the bank’s London branch, had argued he was “dismissed for being too successful” because the bank considered provisions in his contract to be “too generous”.

He had previously told the court that he had been dismissed to avoid paying him huge bonuses after he more than doubled revenues from £183 million to £394 million. He lost his job in 2007, with the bank offering him a £7 million severance offer. He rejected it, claiming he was entitled to more, and went on to challenge the bank, seeking more than £11 million.

Société Générale withdrew its original offer, claiming that, by taking legal action over the size of his payoff, Mr Geys had broken the terms of his contract and so forfeited the money. After appearances at the High Court and Court of Appeal, the Supreme Court has found in his favour.

Four of the five justices on the panel ruled in his favour, with Lady Hale, saying “clear and unambiguous notification” about his dismissal had not been given.

“The bank could easily have done things properly,” she added. “But for whatever reason they did not do so.” In 2010, Mr Geys told the High Court that he was responsible for more than doubling the gross revenue of his division during his three years at the bank.

His lawyers said after yesterday’s ruling that he had been vindicated.

“This successful outcome for Mr Geys vindicates his decision to take his case to the UK’s highest court,” said Tom Custance, partner at the law firm Fox Williams. He added: “Mr Geys is entitled to pursue further claims against Soc Gen for breaches of his contract, which he says occurred before it was terminated.

“Soc Gen had argued that Mr Geys was required to waive those claims as a condition of his receiving the termination payments. However, the Court rejected that argument as it would allow Soc Gen to profit from their own wrongdoing. Mr Geys is therefore entitled both to the termination payments and to pursue his further claims.

“The overall effect of the Supreme Court’s judgment in financial terms is that Mr Geys is entitled to a termination payment of approximately €12.5 million and is able to now pursue further claims against Soc Gen amounting to several million euros.”